This paper argues that Aquinas’ analysis of the passions and their complex relations to perception, activity, and (among humans) judgement offers an illuminating framework for making sense of what we know about the moral emotions in both ourselves and other kinds of animals. On this account, the moral passions play a central and necessary role, both in shaping our overall appraisals of a situation, and moving us to act. Yet human passions cannot function at all, let alone function well, apart from processes of rational formation and integration, which do make a qualitative difference to human morality